The present invention relates to the isomerization of unsaturated alcohols, and more particularly to the isomerization in the presence of a transition metal compound of Groups V, VI and VIII of the Mendeleev Periodic Table as the catalyst of unsaturated alcohols described by the following general formulas (I) and (II) ##STR2## wherein R is a hydrocarbon radical or a substituted hydrocarbon radical, R.sub.2 and R.sub.3 are hydrogen or lower alkyl groups, and R and R.sub.2 may be linked together.
The isomerization reactions of the present invention are equilibrium reactions, and the unsaturated alcohols represented by the general formula (II) may be produced from those of the general formula (I), or conversely, the unsaturated alcohols represented by the general formula (I) may be produced from those of the general formula (II), both processes using the catalysts of the present invention.
As known processes for isomerizing the unsaturated alcohols represented by the general formula (I) into those of the general formula (II), there are exemplified the following:
1. A process of treating the alcohols (I) with a phosphorous halide to give an unsaturated primary halide, reacting it with a salt of an organic acid to give an unsaturated primary ester and hydrolyzing the ester, this process being described in I. N. Nazarov, Izvest Akad. Nauk S.S.S.R., Otdel, Khim. Nauk, 1267 (1957).
2. A process of treating the alcohols of formula (I) with acetic anhydride in the presence of an acid to give an unsaturated primary ester, and thereafter hydrolyzing the ester. This process is described in A. I. Fdoseeva, Sintezy Dashistykh Veshchestv Sbor. State, 257 (1939).
3. A process of treating the alcohols of formula (I) with acetic anhydride in the presence of a base to give an unsaturated tertiary ester, isomerizing the tertiary ester with an acid to give an unsaturated primary ester and hydrolyzing the ester, as described in W. G. Young, J. Am. Chem. Soc. 73:780 (1951); and
4. A process of oxidizing the alcohols of formula (I) to give an .alpha. .beta.-unsaturated aldehyde and selectively reducing the aldehyde, which process is disclosed in M. Stoll, Helv. Chim. Acta. 32:1354 (1949).
On the other hand, for the isomerization of the unsaturated alcohols of formula (II) to yield those of formula (I), the following processes are known:
1. Direct isomerization in the presence of an acid catalyst, such as phosphoric acid, sulfuric acid or boron trifluoride, which is reported by Hirao and Kawanaka in "Discussion With Regard to Perfumes", Terpenes and Essential Oil Chemistry, No. 15; Nov. 2, 1971 in Japan; and
2. Halogenation by means of a hydrogen halide or a phosphorous halide followed by hydrolysis, which is described in Laats, Kand Kogerman, A., Easti NSV Tead. Akad. Toim. Keem Geol., 18, (1) 43, (1969).
These known processes, however, have various drawbacks, such as requiring a large number of steps or proceeding with insufficient selectivity in the various reaction steps because of undesirable side reactions.